Magnapinna pacifica is a species of bigfin squid known only from three immature specimens; two caught at a depth of less than 300 m and one from a fish stomach. M. pacifica is the type species of the genusMagnapinna. It is characterised primarily by its proximal tentacles, which are wider than adjacent arms and bear numerous suckers.

M. pacifica was described in 1998 by Michael Vecchione and Richard E. Young based on three specimens. The holotype is a juvenile specimen of 51 mm mantle length (ML), taken off the Californian coast at a depth of 0–200 m in a Bongo plankton net. The paratype (USNM 885787), a juvenile specimen of 49 mm ML, was found in the stomach of a lancetfish (Alepisaurus ferox). It had initially dried out and was later reconstituted. The third individual, a 19.1 mm ML paralarva, was taken off Hawaii at a depth of 0–300 m in a 4 m2 plankton net.